A car body includes main parts such as an underbody, left and right side members, and a roof panel. For assembling a car body using these parts, firstly the parts to be assembled are positioned relative to each other, using locating jigs, etc. Next, the parts are fixed by spot welding, thereafter re-spot welded to be fixed completely.
A conventional method of assembling a car body utilizes a significantly large locating jig for locating the main parts. For example, a jig used to position the roof panel is larger than the roof panel itself. Such locating jig is installed above the car body assembly line and is movable up and down. When pre-setting the roof panel on the left and right side members, the roof panel is transferred to a position below the locating jig, and set into the locating jig. Next, the locating jig is lowered to position both edges of the roof panel on the upper ends of the side members. Finally, in this manner, the roof panel is spot welded to the side member.
The above-described conventional locating jigs for roof panel are large and heavy, thus cause various problems. For example, conventional jigs tend to require large facility investment at the beginning. Further, it is very complicated to replace the locating jigs corresponding to types of cars to be manufactured. Specifically, the used locating jig should be removed from a hoist and another jig should be set in thereto. During this troublesome operation, the production line may be completely stopped.
Further, a motor for lifting the jig should bear a large load due to the large and heavy locating jig. Thus, a movable portion of the motor may suffer trouble such as wear, so that constant maintenance is needed for working the motor properly. Still further, it is difficult to perform precise location by using large and heavy locating jigs efficiently.